Duckweeds are commonly used as standard ecotoxicological test species and are excellent candidates for phytoremediation due to their adaptability to diverse aquatic conditions. This study investigated the response of two duckweed species, Lemna aequinoctialis and Spirodela polyrhiza, to mercury-contaminated environments, specifically focusing on their growth rates and photosynthetic performance under mercury stress. Duckweeds were treated with HgCl₂ at various concentrations (0, 0.1, 0.2, and 0.3 mg/L) in 10% Hoagland’s medium for seven days, after which growth parameters, pigment contents, and chlorophyll fluorescence levels were evaluated. The results showed that increasing mercury concentrations significantly affected growth and photosynthetic pigments in L. aequinoctialis and S. polyrhiza. Chlorophyll fluorescence analysis indicated that, under higher mercury concentrations, Fv/Fm and Y (II) decreased, while NPQ increased. The findings revealed that L. aequinoctialis was more susceptible to mercury toxicity than S. polyrhiza. Therefore, L. aequinoctialis may serve as a more sensitive species for mercury biomonitoring, whereas S. polyrhiza is more resistant and might, for this reason, be more useful for phytoremediation of mercury-contaminated soil.

This study investigated how postharvest storage temperatures influence the tissue physiology of lemon balm (Melissa officinalis). This herb is used in both fresh and dry forms to prepare functional infusions. Understanding proper raw material storage practices is critical for determining the phytochemical quality of the final product. Fresh bundles were stored at 2, 6, and 20 °C for 15 days, with sampling every 5 days. Tissue gas exchange, color coordinates, and pigments were evaluated alongside the tannin extractability and in vitro antibacterial activity of aqueous infusions. Results demonstrated that ambient storage (20 °C) promoted rapid quality deterioration, characterized by pronounced pigment loss and severe tissue degradation, resulting in poor visual quality by day 15. Deep refrigeration at 2 °C suppressed postharvest physiological activities, limiting cumulative moisture loss to 4.5% while preserving visual freshness and pigment retention. In contrast, mild refrigeration (6 °C) showed the highest weight loss (12.85%) and had the greatest accumulation of phenolic compounds and antioxidant capacity at the storage end. Fresh leaf storage at 2 °C showed the highest tannin extractability in the infusion. Consequently, infusions prepared from these leaves showed the strongest in vitro inhibitory activity against Staphylococcus aureus and Escherichia coli, with the lowest minimum inhibitory concentration and IC₅₀ values. Therefore, storage at 2 °C maintained fresh leaf quality and the phytochemical content of the resulting infusions over the 15-day period tested.

Kale is widely recognized as a nutritional superfood. This study investigated the impact of carbon dioxide (CO₂) concentrations (400, 800, and 1200 µmol mol⁻¹) on the growth, yield, physiological responses, and nutritional contents of two kale cultivars (‘Curly Kale’ and ‘Red Ursa’) grown in a plant factory. A completely randomized design was used to evaluate these parameters. Based on the results, increasing the CO₂ concentration to 1200 µmol mol⁻¹ significantly enhanced stem height, shoot, and root fresh weight and dry weight in ‘Curly Kale’ and ‘Red Ursa’, compared to the other CO₂ concentrations. Increasing CO₂ concentration to 1200 µmol mol⁻¹ significantly enhanced net photosynthesis rate, stomatal conductance, transpiration rate, and water use efficiency in ‘Curly Kale’. In addition, compared to ambient CO₂, the increase in the CO₂ concentration to 800 µmol mol⁻¹ significantly increased the vitamin C, soluble protein, and total phenolic contents, while reducing the nitrate accumulation in both cultivars. However, further elevation to 1200 µmol mol⁻¹ CO₂ markedly decreased the vitamin C content and total amino acids, including both the essential and non-essential amino acids. Among the tested concentration gradients, 800 µmol mol⁻¹ CO₂ was identified as the most cost-effective level for maintaining nutrient density, whereas 1200 µmol mol⁻¹ CO₂ increased unit production costs for ‘Red Ursa’ due to a lack of significant yield returns. In conclusion, enriching the CO₂ concentration to 800 µmol mol⁻¹ provided a balance between improved growth, photosynthetic performance, and optimal nutritional quality, while ensuring economic feasibility and preserving the superfood identity of kale.